A tool-changing arm of the above-mentioned type, when in its gripping position, simultaneously engages the tool which is provided in the spindle and the tool which is provided in the transition position of the tool magazine, through an axial movement of the changing arm pulls both tools from their mountings, by rotation of the changing arms exchanges the places of the tools, and then inserts same again so that the tool removed from the magazine seats in the spindle and the tool removed from the spindle seats in the space of the magazine freed by the aforementioned pulling. After the changing operation, the changing arm can be rotated from its gripping position into a rest position, in which it does not hinder for example the movement of the machine or the accessibility and visibility of the workpiece. Mainly in the case of arrangements with a movable spindle block and a changing arm mounted at a fixed location on the machine and combined for example with the magazine in one structural unit, it is necessary after the changing operation that the changing arm be swung totally out from the space which the drivable spindle block can occupy, in order not to block spindle block movement. The tool-changing arm can very generally have any desired form for example a form which is bent at a certain angle in its turning plane. In most cases, however, it is constructed as a straight changing arm, which is symmetrical with respect to its axis of rotation.
In the case of a tool machine with a spindle block which can be moved horizontally in the axial direction of the spindle, it is already known to arrange the changing arm laterally next to the spindle block ("Modu-line-Machining Center" of the Firm Kearney & Trecker, USA). To enter its rest position, the changing arm is rotated about its axis of rotation until it is positioned vertically, namely, parallel with respect to the side surface of the spindle block. The support for the rotary and shifting movement of the changing arm is also provided next to the spindle block.
Mainly in the case of spindle blocks with a large front surface, the conventional arrangement results in a large distance between the spindle and the possible place for the rotary support of the changing arm. For reasons of symmetry, the distance of the axis of rotation from the tool magazine must be just as large. All together, a changing arm with a large arm length and a large distance between the spindle block and the magazine is thus obtained. Aside from the undesirable large structural dimensions of such machine the large mass and accelerating forces of the tool-holding changing arm are very disadvantageous because they result in longer changing times, greater vibration and greater wear.
A further disadvantage is also seen in the tools, at a large turning radius of the changing arm, being arranged spaced relatively far from one another in the magazine, or as seen in the known machine, the tools have to be swingable by expensive extra structure in the magazine between a storing position and a transfer position, so that the ends of the changing arm do not come into contact with the tools which are adjacent to the tool to be changed.
The purpose of the invention is to provide an improved mechanism of this general type so that the dimensions of the changing arm, and thus also the distance between the tool magazine and the spindle block, can be kept as small as possible.
This purpose is inventively attained by the tool-changing arm being made pivotable about a further pivot axis parallel to the arm axis of rotation, between a rest position and a working position.
Through this inventive construction it is possible to move the axis of rotation, around which rotates the changing arm during the changing operation, into any desired distance from the spindle for the changing operation. Thus, the changing arm can be kept short and the magazine can be arranged very close to the spindle block. After the changing operation the entire changing arm is again pivoted about the pivot axis away from the spindle, until it assumes a position in which it for example no longer hinders the movements of the spindle block. Aside from the reduced structural dimensions of the machine the short changing arm provides also the advantage that the arm can swing into the row of the tools in the magazine despite relatively close arrangement of the tools in the magazine.
According to a further characteristic of the invention, such swinging movement is a pivoting movement. Under the present invention, the changing arm is then pivoted for example from a vertical rest position parallel to the spindle block sidewall to a horizontal working position. The changing arm thus reaches its gripping position during pivoting from its rest position into its working position, so that the pivoting operation does not need any additional time.
In a preferred exemplary embodiment, the changing arm is straight, in a conventional manner, and carries out a 180.degree. rotation during the tool change, wherein the angle of pivoting is for example 90.degree.. The pivot axis is arranged between the axis of rotation and one of the two ends of the changing arm. The arm part which is shorter with respect to the pivot axis is swung during the pivoting movement into the working position toward the tool magazine. This arrangement gives this shorter arm part a turning radius which is again shorter compared with the arm length defined by the axis of rotation, so that the tools can be arranged correspondingly closely in the magazine.
A structural development of the invention provides that the axis of rotation of the tool-changing arm is supported rotatably in a bearing housing, which is pivotable in turn about a pivot axis which is parallel to the axis of rotation and is supported on the machine movably in the direction of said pivot axis. Drives for the rotary movement of the changing arm, the pivoting movement and the shifting movement of the bearing housing are provided. In order to pivot the changing arm from its rest position into the working position, the bearing housing is pivoted and in pivoting thereby takes along with it the axis of rotation. The changing arm remains fixed relative to the bearing housing, so that it also pivots with the bearing housing and thus reaches its gripping position directly, as will be described in more detail in the following detailed description.
Further characteristics and advantages of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings. One exemplary embodiment is illustrated in the drawings and is described in more detail hereinafter.